1). Field of the Invention
This invention relates to a test socket interposer.
2). Discussion of Related Art
To ensure the quality of integrated circuit chips after manufacture, various testing methods have been devised to find defects. Frequently, testing of the electronic device is performed by subjecting it to a set of input conditions. The pass/fail response to these inputs will determine whether it can be delivered to a customer.
Effective testing of an electronic device requires good contact between a signal and ground contact of the electronic device and corresponding contacts on a test socket. During testing, a poor electrical contact may occur between the test socket and the electronic device. One of the reasons for poor electrical contact is non-uniformity of the dimensions of the signal contacts of the electronic device. One or more of the signal contact leads may fail to make full contact with the signal contact of the test socket. Poor electrical contact lowers the reliability of the testing and may impair the transfer of signals between the electronic device and the tester to the extent that a good chip may test as defective.
The invention provides a test socket interposer with a horizontal, nonconductive, flexible substrate with a top and bottom surface, a lower ground contact, and a lower signal contact on the bottom surface of the substrate, positionable on a test socket with the lower ground contact on a socket ground contact and with the lower signal contact on a socket signal contact, an upper ground contact and an upper signal contact on the top surface of the substrate, the upper signal contact having a surface, at least a portion of which (i) is higher than an upper surface of the ground contact so that a signal contact of a device in a common plane as a device ground contact contacts the upper signal contact before the device ground contact contacts the upper ground contact when the device is moved downward, and (ii) is to the right of a lower surface of the lower signal contact so that a downward force exercised by the device signal contact causes pivoting of the upper signal contact that moves the area of contact between the device signal contact and the upper signal contact downward, the substrate being sufficiently compliant to allow for pivoting of the upper signal contact, and for the device ground contact to subsequently contact the upper ground contact, and ground and signal electrical connections, the ground electrical connection linking the upper ground contact with the lower ground contact and the signal electrical connection linking the upper signal contact with the lower signal contact.
The substrate may have at least one tooling hole formed through the substrate for positioning over tooling pins, to position the substrate on the test socket.
The lower surface of the lower ground contact and the lower surface of the lower signal contact may be in a common plane and an air gap may be defined under a portion of the bottom surface of the substrate and above the test socket that is between the socket ground contact and socket signal contact to allow for flexing of the substrate between the lower ground contact and the lower signal contact.
The upper ground contact may be positioned on the top surface of the substrate directly above the lower ground contact.
The distance between the lower surface of the lower ground contact and the bottom surface of the substrate may be the same as the distance between the lower surface of the lower signal contact and the bottom surface of the substrate.
A downward force exercised by the device signal contact on the upper signal contact may cause the upper signal contact to press down against the substrate and form a depression in the top surface of the substrate material under the upper signal contact for the duration that the downward force is exercised.
The depression in the substrate material may be located under the side of the upper signal contact closest to the upper ground contact.
The distance between the upper surface of the upper signal contact and the top surface of the substrate may be greater than the distance between the upper surface of the upper ground contact and the top surface of the substrate.
At least one of the ground electrical connection linking the upper ground contact with the lower ground contact and the signal electrical connection linking the upper signal contact with the lower signal contact may be a via.
The test socket interposer may further include a conductive material filling the void in the via.
The test socket interposer may have a plurality of upper signal contacts.
One of the upper signal contacts may be positioned on the right side of the upper ground contact and one of the upper signal contacts may be positioned on the left side of the upper ground contact.
The upper surface of the upper signal contact on the right side and the upper surface of the upper signal contact on the left side may be the same distance above the top surface of the substrate.
The upper surfaces of the upper signal contacts may be higher than the upper surface of the upper ground contact so that a device including a signal contact on the right side of the device, a signal contact on the left side of the device, and a ground contact in a common plane with the device signal contacts, will make contact with the right and left upper signal contacts before the upper surface of the upper ground contact.
A downward force exercised by the right and left device signal contacts on the right and left upper signal contacts may cause pivoting of the upper signal contacts that moves the areas of contact between the right and left device signal contacts and the upper signal contacts downward, the substrate being sufficiently compliant to allow for pivoting of the upper signal contacts, and for the device ground contact to subsequently contact the upper ground contact.
A plurality of upper signal contacts may be all positioned on a perimeter of an area on the top surface of the substrate and the upper ground contacts may be all positioned on the top surface of the substrate in the area within the upper signal contacts.
At least two of the upper signal contacts may be in a line on the right side of the area and at least two of the upper signal contacts may be in a line on the left side of the area.
The invention also provides a test socket interposer with a horizontal, non-conductive, flexible substrate with a top and bottom surface, a lower ground contact and a lower signal contact on the bottom surface of the substrate, positionable on a test socket with the lower ground contact on a socket ground contact and with the lower signal contact on a socket signal contact, an upper ground contact and an upper signal contact on the top surface of the substrate, the upper signal contact having a surface, at least a portion of which (i) is higher than an upper surface of the ground contact and so that a signal contact of a device in a common plane as a device ground contact contacts the upper signal contact before the device ground contact contacts the upper ground contact when the device is moved downward, (ii) is located vertically above the top surface of the substrate a greater distance than the height of the upper ground contact measured from the top surface of the substrate, and (iii) is to the right of a lower surface of the lower signal contact so that a downward force exercised by the device signal contact causes pivoting of the upper signal contact by pressing the upper signal contact down against the substrate and forms a depression in the top surface of the substrate material under the upper signal contact allowing the area of contact between the device signal contact and the upper signal contact to move downward, the substrate being sufficiently compliant to allow for pivoting of the upper signal contact, and for the device ground contact to subsequently contact the upper ground contact and a ground and signal electrical connection in the substrate, the ground electrical connection linking the upper ground contact with the lower ground contact and the signal electrical connection linking the upper signal contact with the lower signal contact.
The invention further provides a method for testing a device using an interposer, the device having a signal contact and a ground contact, and the interposer having a substrate, a lower ground contact, a lower signal contact, an upper ground contact and an upper signal contact, including positioning the interposer on the test socket, moving a device downward until the device signal contact makes contact with the upper surface of the upper signal contact and before the device ground contact makes contact with the upper ground contact, exerting a downward force on the upper signal contact with the device signal contact to cause pivoting of the upper signal contact, the substrate material being sufficiently compliant to allow for a portion of an area of contact of the device and the upper signal contact to move downward to allow subsequent contact of the device ground contact with the upper ground contact and conducting electricity between the device and the test socket via the contacts.